Composite materials, such as fiber-reinforced composite materials, have become popular as a constituent of high-performance products and components that need to be lightweight, yet strong enough to take harsh loading conditions and stresses. Examples of such applications are components used in aerospace applications; the tails, wings, fuselages, and propellers of aircraft; boats and other marine vessels; bicycle frames; and car bodies. Modern jet aircraft include fuselages composed largely of composites. Carbon fiber-reinforced polymers (CFRPs) are used in the fuselage of aircraft and space vehicles.
One type of composite material is a lay-up comprised of a honeycomb core sandwiched between two outer skin layers above and below the honeycomb core. The entire sandwich may be made of a material such as fiberglass or a CFRP, or combinations of the two. Other forms of composite materials include a fiberglass or CFRP honeycomb core between outer skin layers of aluminum.
Such composite materials used in vehicles such as aircraft and spacecraft are subjected to shock loading, blunt and sharp impacts, repeated bending and torsional loading, and temperature extremes. Composite material may sustain damage from such use, and the damage may not be apparent from a visual inspection. For example, damage may take the form of delamination, that is, a separation between the core and outer skin of a laminate, or a crushed core, or a disbonding.
Testing is necessary to determine whether such damage has been sustained by the composite material. However, such testing must be non-destructive so that the structural integrity of the composite material to be tested must not be compromised, or compromised further, as a result of the testing. It also is desirable to test the composite structure in situ for efficiency reasons.
Consequently, non-destructive testing systems have been developed. One such system, disclosed in U.S. patent application Ser. No. 13/977,319 filed Sep. 4, 2013 and titled METHOD AND APPARATUS FOR DEFECT DETECTION IN COMPOSITE STRUCTURES, discloses a method and apparatus for defect detection in composite structures. That system and method utilize a “pitch-catch” probe connected to a control box that is controlled by a laptop computer or other computing device. The pitch-catch probe includes two transducers: a first transducer that transmits an ultrasonic signal to and through the surface of the composite material to be tested, and a second transducer that receives the ultrasonic signal. The alteration of the frequency and amplitude of the received ultrasonic signal is processed by the control box to determine the presence of a defect. Further, variations in the received ultrasonic signal may be matched with a library of known signals for that particular composite material being tested, so that the received signal can be used to determine a type of defect in the composite material.
In order to use such non-destructive inspection devices efficiently over a large area, such as may be found on an aircraft fuselage made of composite material, there is a need to provide a scanning platform that is capable of optimizing the accuracy and consistency of the data gathered by the non-destructive inspection device.